In a wet type developing apparatus of this sort, a liquid developer reserved in a liquid developer tank is drawn up by a liquid developer supply roller onto a developing roller and, with the liquid developer fed on the surface of the developing roller, an electrostatic latent image formed on the surface of a photoconductor drum is developed into a toner image. And, the toner image on the photoconductor drum is transferred on a printing surface of web directly or via a transfer roller.
In a conventional wet type developing apparatus as mentioned above, use has been made of an anilox roller as the liquid developer supply roller immersed in part in the liquid developer tank. By varying the peripheral speed of the liquid developer supply roller with respect to that of developing roller, the rate of feed, or the supply, of the liquid developer onto the developing roller is varied. See, for example, JP 2008-299065 A).
In the conventional apparatus using the anilox roller in which the anilox roller is immersed in the liquid developer of the liquid developer tank to draw up the liquid developer, the problem arises that the higher the speed of rotation of the liquid developer supply roller, the more does air that has come into cells on the surface of the anilox roller fail to come out completely, and air residual in the cells of the liquid developer supply roller tends to get mixed into the liquid developer fed on the developing roller, which causes instabilizing the supply or rate of feed, of the liquid developer onto the developing roller.